Reducing incremental measurement sensor error

ABSTRACT

For position sensors, e.g., a fiber-based system, that build a shape of an elongated member, such as a catheter, using a sequence of small orientation measurements, a small error in orientation at the proximal end of the sensor will cause large error in position at distal points on the fiber. Exemplary methods and systems are disclosed, which may provide full or partial registration along the length of the sensor to reduce the influence of the measurement error. Additional examples are directed to applying selective filtering at a proximal end of the elongated member to provide a more stable base for distal measurements and thereby reducing the influence of measurement errors.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/844,420, filed Dec. 15, 2017, which is a continuation of U.S. patentapplication Ser. No. 15/387,347, issued as U.S. Pat. No. 9,844,353,filed Dec. 21, 2016, which is a continuation of U.S. patent applicationSer. No. 15/076,232, filed Mar. 21, 2016, which is a continuation ofU.S. patent application Ser. No. 14/712,587, issued as U.S. Pat. No.9,289,578, filed May 14, 2015, which is a continuation of U.S. patentapplication Ser. No. 14/208,514, issued as U.S. Pat. No. 9,057,600,filed Mar. 13, 2014, which claims benefit of U.S. Provisional PatentApplication No. 61/779,742, filed Mar. 13, 2013. The contents of all ofthe above-referenced patent applications are hereby incorporated byreference in their entirety and for all purposes.

BACKGROUND

Currently known minimally invasive procedures for diagnosis andtreatment of medical conditions use shapeable instruments, such assteerable devices, flexible catheters or more rigid arms or shafts, toapproach and address various tissue structures within the body. Forvarious reasons, it is highly valuable to be able to determine the3-dimensional spatial position of portions of such shapeable instrumentsrelative to other structures, such as the operating table, otherinstruments, or pertinent anatomical tissue structures. Such informationcan be used for a variety of reasons, including, but not limited to:improve device control; to improve mapping of the region; to adaptcontrol system parameters (whether kinematic and/or solid mechanicparameters); to estimate, plan and/or control reaction forces of thedevice upon the anatomy; and/or to even monitor the systemcharacteristics for determination of mechanical problems. Alternatively,or in combination, shape information can be useful to simply visualizethe tool with respect to the anatomy or other regions, whether real orvirtual.

In many conventional systems, the catheter (or other shapeableinstrument) is controlled in an open-loop manner, as described in U.S.patent Ser. No. 12/822,876, issued as U.S. Pat. No. 8,460,236, thecontents of which are incorporated by reference in its entirety.However, at times the assumed motion of the catheter does not match theactual motion of the catheter. One such reason for this issue is thepresence of unanticipated or un-modeled constraints imposed by thepatient's anatomy. Another reason for this may be that the parameters ofthe tool do not meet the ideal/anticipated parameters because ofmanufacturing tolerances or changes in the mechanical properties of thetool from the environment and aging.

Thus to perform certain desired applications, such as, for example,instinctive driving, shape feedback, and driving in a fluoroscopy viewor a model, there exists a need for tool sensors to be properlyregistered to the patient in real time. Moreover, there remains a needto apply the information gained by spatial information or shape andapplying this information to produce improved device control or improvedmodeling when directing a robotic or similar device. There also remainsa need to apply such controls to medical procedures and equipment.

Localization sensors such as fiber optic shape sensors may includeIncremental Measurement Sensors (IMSs). An IMS measures a shape or pathof an elongate member by combining a sequence of serial orientation anddistance measurements. For instance, FOSSL generates a shape bymeasuring types of strain at discrete points in the fiber; this strainis then translated to the incremental change in roll and bend, which isincremented along all steps to obtain the position and orientation at agiven location. As a result, each position and orientation at a point isdependent on the position and orientation of all proceeding points. Incontrast, an electromagnetic coil sensor measures position at pointsalong the elongate member independent of any other measurements.

One drawback of IMSs is that a measurement noise (error) at any locationalong the path may propagate to all measurements distal to thatmeasurement. While these errors are implicit in the nature of thesensor, orientation errors at a proximal portion of the IMS may resultin a large position error at the distal end of the elongate member. Inapplications that include accurate distal position measurements, thiscan cause the measured tip position to vary greatly between successivemeasurements due to noise at a single point in the proximal portion. Oneway of thinking about the issue is to consider the IMS length as a leverarm—small rotations at one end cause large changes in the position atthe other end. The longer the lever arm, the more pronounced theconversion from proximal orientation error to distal position error. Itshould be noted that an orientation error at the proximal end will nottend to cause a large orientation error at the distal end becauseorientation errors themselves accumulate (sum) over the length of thesensor.

Thus, for Incremental Measurement Sensors that build a shape using asequence of small orientation measurements, a small error in orientationat the proximal end of the sensor will cause a large error in positionat distal points on the fiber. Accordingly, there is a need for animproved method of using IMSs that reduces measurement errors.

SUMMARY

Exemplary systems and methods are disclosed for reducing measurementerror, e.g., relating to position measurements of an elongated member,e.g., along a distal portion of the elongated member. An exemplarymethod includes providing an incremental sensor measurement at a distalposition on an elongated member, and applying registration data at oneor more proximal locations along the elongated member. This exemplarymethod may further include determining a position of the incrementalmeasurement sensor based at least upon the registration data from theone or more proximal locations.

In another exemplary method, either alternatively or in addition to theabove-described registration data, a proximal signal of the elongatedmember may be selectively filtered, e.g., in comparison to a distalportion of the elongated member. In such examples, a distal position ofthe incremental measurement sensor may be determined based at least uponthe filtered proximal signal, thereby reducing a fluctuation of thedetermined distal position of incremental measurement sensor.

An exemplary measurement system may include an incremental sensormeasurement positioned at a distal position on an elongated member, anda processor. In some exemplary approaches, the processor may beconfigured to apply registration data at one or more proximal locationsalong the elongated member, and to determine a position of theincremental measurement sensor based at least upon the registration datafrom the one or more proximal locations. In other examples, eitheralternatively or in addition to relying upon registration data, theprocessor may be configured to selectively filter a proximal signal ofthe elongated member, and determine a position of the incrementalmeasurement sensor based at least upon the filtered proximal signal.

BRIEF DESCRIPTION OF THE DRAWINGS

While the claims are not limited to a specific illustration, anappreciation of the various aspects is best gained through a discussionof various examples thereof. Referring now to the drawings, exemplaryillustrations are shown in detail. Although the drawings represent theillustrations, the drawings are not necessarily to scale and certainfeatures may be exaggerated to better illustrate and explain aninnovative aspect of an example. Further, the exemplary illustrationsdescribed herein are not intended to be exhaustive or otherwise limitingor restricted to the precise form and configuration shown in thedrawings and disclosed in the following detailed description. Exemplaryillustrations are described in detail by referring to the drawings asfollows:

FIG. 1A illustrates a variation of a localization system in a typicaloperation room set up.

FIG. 1B illustrates a 3D Model frame.

FIG. 2 illustrates an exemplary robotic surgical system.

FIG. 3 is a schematic representation of a first registration techniqueof correlating a sensor reference frame to selective reference frames.

FIG. 4 is a flow chart that illustrates a method of transforming areference frame for a sensor of a surgical tool into a target referenceframe.

FIG. 5 is a flow chart that illustrates a method of transforming areference frame associated with a tool into a target reference frame.

FIG. 6 is a flow chart that illustrates a method of transforming areference frame associated with a tool into a target reference frameutilizing medical appliances.

FIG. 7 is a flow chart that illustrates a method of using a sensor totransform a reference frame associated with a tool into a targetreference frame.

FIG. 8 is a schematic illustration of a method of using an intravascularimaging sensor coupled with a shape sensor to transform a referenceframe associated with a tool into a target reference frame.

FIG. 9 is a schematic illustration of an exemplary elongate member,e.g., a fiber, having a proximal end and a distal end.

FIG. 10 is a schematic illustration of another exemplary elongate memberhaving a distal end inserted into a patient, with a proximal endremaining outside the patient.

FIG. 11 is a process flow diagram for an exemplary process of reducingmeasurement error associated with the position of an elongate member.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary approaches described herein provide full or partialregistration along the length of a sensor to reduce the influence ofmeasurement error. As will be described further below, an exemplaryregistration process generally relates a reference frame of a sensor toanother reference frame of interest. Alternatively or in addition toexamples employing full or partial registration along the length of asensor, applying heavier filtering at the proximal end of the sensor canprovide a more stable base for distal measurements reducing theinfluence of measurement errors. While these exemplary approaches arediscussed in the context of a Fiber Optic Shape Sensing and Localization(FOSSL) system, other visualization methodologies may be employed. Fiberoptic shape sensing is a technology that can sense the shape of aflexible body such as a catheter during a surgical procedure to permitvisualization of the catheter in the patient's anatomy.

One exemplary methodology provides a solution to this problem by usingpoint registration along the length of the fiber to reduce the effect ofthe lever arm problem. As noted above, these techniques apply to allsensors that use incremental measurements, but nevertheless exemplaryapproaches below are described generally in the context of FOSSL fibertechnology.

Another exemplary approach includes applying registration data along thefiber as well as at the proximal attachment to reduce error.Additionally, in another example stronger filtering may be utilized onthe proximal orientation signal to reduce noticeable fluctuation of theposition distally.

In still another exemplary illustration, orientation error at theproximal end of an IMS is decoupled from position error at the distalend. Exemplary methods of decoupling this error include providing somenotion of a registration closer to the distal tip and reduce the effectof orientation error.

Various localization systems and methods for tracking an elongateinstrument or tool, e.g., a robotically controlled elongate instrument,in real time, in a clinical or other environment, are described herein.The term “localization” is used in the art in reference to systems fordetermining and/or monitoring the position of objects, such as medicalinstruments or tools in a reference coordinate system. Variousinstruments are contemplated for use in the various systems describedherein. In one exemplary arrangement, elongate instruments arecontemplated, such as, e.g., a catheter or vascular catheter. Thevarious methods and systems may include integrating or registering alocalization system or a localization sensor coupled to a surgical tool,with an image. A fiber optic tracking or localization system is justone, non-limiting example of a system that allows for the tracking of alocation, position and/or orientation of a localization sensor placed.Various other localization sensors may be utilized, e.g.,electromagnetic sensors, and other sensors for detecting or controllingthe movement of medical equipment. When the localization sensor isintegrated into an image, it enhances the capabilities of an instrumentcontrol or tracking system by allowing a user or doctor to easilynavigate the instrument through the complex anatomy without exposing thepatient to excessive radiation over a prolonged period of time.

The localization data or tracking information of a localization sensormay be registered to the desired image or model to allow for navigationof an elongate instrument through the image or model to accuratelyrepresent movement of the elongate instrument within a patient. As notedabove, registration is a process that generally requires relating areference frame of a sensor to another reference frame of interest. Ifthe positions, orientations or shapes of two or more objects are knownin the same reference frame, then the actual positions, orientations orshapes of each object relative to each other may be ascertained. Thus,with this information, one can drive or manipulate one of the objectsrelative to the other objects.

In most interventional procedures, the reference frame of interest isthe visualization frame. The reference frame is the frame that thedoctor is viewing, such as a patient or a live 2D/3D image suchfluoroscopy, ultrasound or others. Thus, the goal of registration is todetermine the relationship of a frame of a sensor integrated into a toolor element in the surgical suite within the frame of reference of thepatient, as represented in a 2D/3D image.

When the tool is registered to a 3D model, the user can drive andmanipulate the tool in the 3D model. This technique provides anadvantage in that there is no longer a need for live fluoroscopy andradiation during a procedure. The tool is localized to the 3D model andthe position, shape and orientation of the tool is visible to the user.Since the tool position, shape and orientation is updated in real timeby a localization sensor, an image of the tool in the virtualrepresentation of the 3D model will be updated as it is being advancedinto the patient. The sensor is localized to the reference frame of the3D model; therefore the orientation of a tip of the tool is knownrelative to the 3D model. This enables driving of the tool (such as acatheter) within 3 dimensional views of the anatomy and hence improvesvisualization and control during a surgical procedure.

As discussed above, exemplary sensors may include incrementalmeasurement sensors, where the position and orientation of a particularpoint is calculated and dependent on the previously calculatedorientations and positions of proximal points or (spacing of consecutivepoints). Thus, the localization sensor operating in any medical systemneeds to be registered with a coordinate system, frame or image that isuseful to an operator, such as the pre-operative 3D model or afluoroscopic image. For incremental measurement sensors, suchregistration is challenging because the coordinate system or frame ofthe sensor is not always easily related to the coordinate system ofinterest (i.e., the pre-operative 3D model).

Moreover, the relationship between the sensor and the coordinate systemof the interest may change over time during a procedure. For example, inone exemplary robotic system, a fiber optic sensor may have itsreference frame based physically in a splayer (base) for a catheter.Thus, as the splayer is robotically driven during a surgical procedure,the position and orientation of the base of the fiber will change withrespect to other reference frames.

In addition to changing positions of reference frames, the registrationprocess often requires information about the imaging system providingthe image, such as its physical dimensions and/or the details about theimaging techniques used to acquire a particular 3D model or other image.Due to the variability in equipment used in a clinical environment, incertain situations there may be no guarantee that such information willbe available or easily obtainable to an outside party.

As such, various techniques to estimate system parameters and variousregistration techniques may help facilitate the clinical use oflocalization technology.

In certain variations, a method for tracking a robotically controlledelongate instrument in real time may include displaying an image of apatient's anatomy. A localization sensor may then be coupled to therobotically controlled instrument. The localization sensor may providelocalization data of the sensor and/or instrument. Moreover, differentsensors may be registered to specific tools, thereby enabling tooldifferentiation. The localization data from the localization sensor maybe registered to the image. Registering may include transforminglocalization data generated by the localization sensor to the coordinatesystem or frame of the image such that localization data of the elongateinstrument, to which the localization sensor is coupled, is overlaid onthe image. The coordinate system of the localization sensor may betransformed or translated to the coordinate system of the image throughone or more transformations, and optionally through other coordinatesystems, to register the localization data to the image. As a result, acontinuously or substantially continuously updated location of at leasta portion of the elongate instrument is provided in the image of theanatomy of a patient, which allows for or facilitates robotic navigationor control of the elongate instrument through the anatomy e.g., throughthe vasculature of a patient.

The location, position and/or orientation of the localization sensor maybe continuously tracked to allow for accurate manipulation of theelongate instrument in or through the anatomy of a patient. Varioustypes of images may be utilized in the methods and systems describedherein. For example, an image may be generated by CT or 2D or 3Dfluoroscopy. An image may include a 3D or 2D anatomical model or a 2D or3D fluoroscopic image or other types of images useful for visualizing ananatomy of a patient to perform various medical procedures.

When using a fluoroscopy image, an image intensifier may be utilized.Localization data from the localization sensor may be registered to afluoroscopy coordinate system of a fluoroscopy image coupled to theimage intensifier. In order to register the localization data from thelocalization sensor to the fluoroscopy image, various parameters may beascertained or known. For example, such parameters may include: adistance from an X-ray source to the image intensifier, a distance fromthe source to a bed, a size of the image intensifier, and/or the axis ofrotation of a C-arm of the fluoroscopy system.

In certain variations, localization data can be registered to a 3Danatomical model or a fluoroscopy image. The techniques used to performthe registration vary depending on the target. Where localization datais registered to a fluoroscopy image, the 2D nature of the fluoroscopyimages may require that multiple images be taken at different anglesbefore the registration process is complete.

FIG. 1A is a schematic of a typical operation room set up for a roboticsurgical system. More specifically, a typical robotic surgical system 10includes a table 12 upon which a patient 14 will be placed, afluoroscopy system 16, and a surgical tool, such as a catheter 18 (bestseen in FIG. 2). Attached to the table 12 is a setup joint arm 20 towhich a remote catheter manipulator (RCM) 22 is operatively connected. Asplayer 24 may be mounted to the RCM 22. A surgical tool, such as acatheter, is operatively connected to the splayer 24. A fiber sensor 26may be operatively connected to the surgical tool. The fluoroscopysystem 16 includes a C-arm 28. A fluoroscopy panel 30 is mounted to theC-arm 28. The C-arm is selectively moveable during the procedure topermit various images of the patient to be taken by the fluoroscopypanel 30.

Additional portions of the robotic surgical system 10 may be furtherseen in FIG. More specifically, robotic surgical system 10 may furthercomprise an operator control station 31, which may be remotelypositioned with respect to table 12. A communication link 32 transferssignals between the operator control station 31 and the RCM 22. Theoperator control station 31 includes a control console 34, a computer36, a computer interface, such as a mouse, a visual display system 38and a master input device 40. The master input device 40 may include,but is not limited to, a multi-degree of freedom device having multiplejoints and associated encoders.

Each element of the robotic surgical system 10 positioned within theoperating suite may define a separate reference frame to which sensorsmay be localized. More specifically, separate reference frames may bedefined for each of elements of the robotic surgical system 10. Suchreference frames may include the following: a table reference frame TRFfor the table 12, a setup joint frame SJF for the setup joint 20, an RCMreference frame RRF for the remote catheter manipulator (RCM) 22, asplayer reference frame SRF, a fluoroscopy reference frame FF. Separatereference frames may also be defined for a patient—patient referenceframe PRR, a reference frame FRF for a sensor disposed within a surgicaltool, and a pre-operative 3D frame AMF (best seen in FIG. 1B).

To relate a coordinate frame of a fiber optic sensor of a tool to eithera fluoroscopy frame FF, or a pre-operative 3D frame AMF, a variety ofregistration techniques may be employed. Generally, the techniquesproposed herein fall into several categories. A first category involvesusing image processing or vision techniques to relate a reference frameRFR of a fiber sensor directly to an image or 3D model. This techniquemay be accomplished manually by a user or done automatically using imageprocessing techniques. Another category to coordinate the referenceframe FRF of a fiber optic sensor involves using knowledge abouthardware, and potentially other sensors and or position of the fiber.Further discussion of these techniques is set forth below.

Registration to Fluoroscopy Coordinate Frame

Referring to the systems illustrated in FIGS. 1-3, the first category ofregistration techniques will now be described. The first categoryrelates the coordinate system of the sensor reference frame FRF to afluoroscopy reference frame FF directly. This technique utilizesfluoroscopy images taken during the surgical procedure by thefluoroscopy system 30, in real-time.

More specifically, an exemplary registration process 200 is illustratedin the flow chart of FIG. 4. The process 200 may begin by inserting atool into a patient at block 202. As described above, in one exemplaryconfiguration, the tool is a catheter 18, which may be inserted by anRCM 22. Next, at block 204 an intra-operative image is taken of the tool18.

In one exemplary arrangement, the intra-operative image is a fluoroscopyimage taken by fluoroscopy system 30. Next, distinctive elements of thetool may be identified in the fluoroscopy image at block 206. In oneexemplary configuration, the block 206 may be accomplished byinstructing the user to select certain marked points of a catheter 18 inthe fluoroscopy image at the work station 31. Examples of marked pointsinclude, but are not limited to, physical features of the catheter 18such as the tip of the catheter 18, certain shapes and an articulationband. In other exemplary configurations, fluoroscopy markers may bedisposed on the catheter.

Once the selected points are identified in the fluoroscopy image, in thenext step 208, coordinates of the selected points of the catheter 18 maybe compared to corresponding measured points of elements of thecatheter. In one exemplary configuration, measured points from a toolsensor operatively connected to the tool 18 may be used. Morespecifically, in one exemplary configuration, the tool sensor is a fiberoptic sensor. Information about the fiber optic sensor will be known inrelation to the features on the catheter from an in-factory calibration.This comparison can be used to determine a transformation matrix thatcan be used to transform a reference frame FRF for a sensor disposedwithin the surgical tool into the fluoroscopy reference frame FF. Thistransformation then localizes the tool relative to the intra-operativefluoroscopy image.

Once the fiber sensor of the tool has been registered or localized tothe fluoroscopy image, the tool operator can now move or drive the toolto various, desired points visualized in the fluoroscopy image.Moreover, the computer 36 may be configured to track the marked pointsover time, such that an appropriate transformation may be updated.

In one exemplary configuration, the identifiable markers need not be onthe portion of the tool that is inserted into the patient. For example,markers may be embedded on a splayer 24, which may allow for larger andmore complex markers to provide enhanced registration capabilities.

As described above, in addition to utilizing fluoroscopy marked points,it is also contemplated that distinct shapes that may be visible underfluoroscopy may also be used. However, this technique will require someimage segmentation (to identify and separate out targeted shapes).

With respect to the proposed technique of localizing a sensor referenceframe FRF to the fluoroscopy reference frame FF, the localization sensorcould serve to reduce the use of fluoroscopy during a procedure. Morespecifically, the use of fluoroscopy would be reduced since fluoroscopywould only be required when re-registration is needed during theprocedure due to the loss of accuracy in the data obtained from thesensor.

In certain arrangements, it may be desirable to further register thetool to a 3D model reference frame AMF, as illustrated in FIG. 3.Registration to the 3D Model is discussed more fully below.

Registration Through Successive Physical Components

Another exemplary technique proposed to register a tool 18 to a desiredreference frame involves the use of physical components of the medicalsystem 10 and multiplying successive transformations. This proposedtechnique 300 is illustrated schematically in FIG. 5 and involvesfinding a transformation path from a tool reference frame such as afiber sensor, splayer 24, or catheter 18, to the table 12, as in mostsurgical suite setups, the table location is generally known withrespect to the fluoroscopy system 30. More specifically, registrationtechnique 300 involves determining a tool reference frame at block 302(where the tool reference frame may be defined as the sensor referenceframe FRF, splayer reference frame SRF or a catheter reference frame)and correlating the tool reference frame to a table reference frame TRFat block 304, thereby registering the tool 18 to the table 12.Registering the tool 18 to the table 12 will serve to provide necessaryinformation to permit registration to an additional target frame, suchas a fluoroscopy reference frame FF, for example. Because the table 12location is typically known with respect to a fluoroscopy system 30, acomparison of set reference points of the table 12 with correspondingreference points in a fluoroscopy image may be used to determine atransformation matrix to transform the table reference frame TRF intothe fluoroscopy reference frame FF. The tool 18 is registered to thetable reference frame TRF, and thus combining all three transformationslocalizes the tool relative to the intra-operative fluoroscopy image.

However, it is understood that the present disclosure does not requirethat the tool 18 be registered to the table 12. Indeed, it is expresslycontemplated that registration of the tool 18 to other physicalcomponents within the surgical suite may also be utilized. This proposedtechnique requires the use of other sensors in addition to, oralternative to a fiber sensor, however. Exemplary configurations ofregistration through physical surgical suite components are discussed infurther detail below.

One exemplary method of performing registration through successivephysical components is illustrated in the flow chart in FIG. 6. In thistechnique, the registration process 400 begins at block 402, withdetermining the location of the setup joint 20 with respect to the table12. Encoders on the RCM 22 and setup joint 20, with kinematic models maybe used to determine the location of the setup joint 20 with respect tothe table 12. More specifically, the encoders assist with determiningthe location of the RCM 22 with respect to the table 12. With thelocation value of the position that the setup joint 20 is fixed to thetable 12, the location of the splayer carriage 24 carried by the RCM 22with respect to the table 12 can be determined; i.e., the setup jointreference frame SJF is localized with the RCM reference frame RRF.Because information about the catheter will be known in relation to thesplayer carriage 24 from an in-factory calibration, at block 404 of theregistration process 400, an evaluation of the splayer carriage 24information with respect to the RCM can be used to determine atransformation matrix that can be used to transform the splayer carriagereference frame SRF to the table reference frame TRF. As describedabove, because the table 12 location is known with respect to thefluoroscopy system 30, at block 406 another transformation may be donefrom the table reference frame TRF to the fluoroscopy reference frameFF. This final transformation, i.e., from the table reference frame TRFto the fluoroscopy reference frame FF, then localizes the tool relativeto the intra-operative fluoroscopy image.

In another exemplary method of performing registration throughsuccessive physical components, inertial sensors on the RCM 22, coupledwith the information about the initial position of the RCM 22 on thetable 12, may be used to assist in localizing the catheter splayerreference frame SRF to the table reference frame TRF. More specifically,once the RCM 22 is localized to the table reference frame TRF, thecatheter splayer reference frame SRF may be localized to the tablereference frame TRF, as the position of the catheter splayer 24 withrespect to the RCM 22 will be known from in-factory calibration.

Yet another exemplary method 500 of performing registration throughphysical components is illustrated in FIG. 7. The method 500 uses asecond fiber optic sensor. In a first step 502, one end of the fiberoptic sensor is fixed to the table 12. Next, in step 504, the other endof the sensor is fixed to the splayer 24 in a knownorientation/position. In this technique, a position and orientationtransformation between the tip and base of the fiber sensor may bedetermined, thereby localizing the catheter splayer reference frame SRFto the table reference frame TRF in step 506. However, it is understoodthat the initial position of the fixed point at the table must be known.Once the catheter splayer reference frame SRF is localized to the tablereference frame TRF, because the table 12 location is known with respectto the fluoroscopy system 30, in step 508 another transformation may bedone from the table reference frame TRF to the fluoroscopy referenceframe FF. This final transformation, i.e., from the table referenceframe TRF to the fluoroscopy reference frame FF, then localizes the toolrelative to the intra-operative fluoroscopy image.

A further exemplary method of performing registration of a surgical toolto a physical component includes using electromagnetic sensors to trackthe location of the splayer 24 with respect to an electromagnetic sensorat a known location on the table 12. In using this technique, becausethe tool location is calibrated to the splayer 24 in the factory, oncethe splayer 24 is localized to the table reference frame TRF, the toolmay be localized to the fluoroscopy reference frame FF as the table 12is known with respect to the fluoroscopy system 30.

In yet another exemplary method, instead of electromagnetic sensors,overhead cameras or other visualization techniques may be employed totrack distinct features on the splayer 24 and the table 12 to determinethe respective orientation and position with regard to each other.

A further technique may use the range sensors (such as, e.g., IR orultrasound) to find the distance to several distinct and predeterminedpoints on the table 12 and the splayer 24. Once the splayer 24 islocalized to the table reference frame TRF, the tool may be localized tothe fluoroscopy reference frame FF as the table 12 is known with respectto the fluoroscopy system 30.

All of the above techniques serve to register the tool to a physicalcomponent within the surgical suite, such as, for example, the table 12.Some of the above techniques require the RCM 22 and setup joint 20 to beregistered to the table 12. That pre-registration step may be achievedby using some known feature on the table 12 that the setup joint 20 mayreference. Additionally, the pre-registration step may be achieved ifthe setup joint is equipped with joint sensors such as encoders. Inanother exemplary configuration, the tip of a sensor equipped tool maybe used to touch or register the known feature on the table 12 to locatethe table 12 with respect to other equipment within the surgical suite.

The kinematics of the RCM 22 can also be calculated by holding the tipof a fiber optic equipped tool in an arbitrary fixed location andcycling through the various axes of the RCM 22. By keeping the tip in afixed location, the relative changes to the fiber origin can beobserved, and thus the kinematics of the system can be determined andlocalized to the table 12. Once localized to the table reference frameTRF, the tool may then be localized to the fluoroscopy reference frameFF, as discussed above.

In addition to adding the sensors discussed in the above techniques,additional modifications may be made to the location of the fiber baseto facilitate registering the fiber sensor to the physical structurewithin the suite, such as, for example, the table 12. For example, onemodification is to extend the length of a fiber in the catheter so thatthe origin/base can be extended out of the splayer 24 and attached to afixture having a known location on the table 12. Once localized to thetable reference frame TRF, the tool may then be localized to thefluoroscopy reference frame FF, as discussed above.

Registration to a 3D Model

Registration of the tool to a 3D Model is also contemplated in thisdisclosure. Such registration may be performed directly from the fibersensor reference frame FRF to the 3D Model frame AMF. In one exemplarytechnique, the operator is utilized. When the tool (such as thecatheter) is inserted into the patient, tortuosity can be visualizedfrom the fiber sensor data, as well as on the pre-operative 3D Model. Toregister the tool in the 3D Model, the operator may translate and rotatethe 3D Model so that distinct images and/or features in the tortuositymatch or line up with the shape of the fibers. However, in using thistechnique, every time the patient moves, the tool should bere-registered.

In another exemplary arrangement, rather than having an operatormanually match features in the tortuosity, in one technique, a computeralgorithm such as automated geometric search or mathematicaloptimization techniques that segments the model and matches the modeland tool shape dynamically may also be used to match various shapes orfeatures from the fiber sensor to the 3D pre-operative Model. However,if the patient moves, even slightly, the 3D Model could bemis-registered. Thus, the algorithms may be used to re-register the toolautomatically or the user could use an input device, such as a trackball or mouse to move the 3D Model manually.

Another proposed technique may be used to register the fiber sensor tothe 3D Model through the fluoroscopy image, as illustrated in FIG. 3. Inthis technique, any of the above described techniques for registeringthe surgical tool 12 to the fluoroscopy reference frame FF may beutilized. To register the fluoroscopy reference frame FF to the 3D Modelreference frame AMF, in one exemplary configuration, specific anatomicallandmarks may be used to provide recognizable reference points. The onlyrequirement for this approach is to have an anatomical landmark that isrecognizable in both the fluoroscopy reference frame FF, as well as thepre-operative 3D Model reference frame AMF. Once the recognizable pointis identified in the fluoroscopy image, the 3D Model may then be rotatedby the operator to line up the recognized points in the fluoroscopyimages with the 3D Model images. This action serves to register thefluoroscopy reference frame FF to the frame of the 3D Model AMF. As thetool has previously been localized to the fluoroscopy reference planeFF, so once the fluoroscopy reference plane FF is registered, the tool'slocation within the patient's anatomy may be determined with referenceto the 3D Model localizing the tool to the 3D Model. In one exemplaryconfiguration, a visual representation of the tool, based on thetransformation matrix, may be displayed on the 3D Model. In this manner,the tool operator may then navigate the tool through the 3D Model.

While certain of the above described techniques utilized distinct markedpoints of a tool, such as a medical catheter, to register the tool withthe fluoroscopy image, it is also understood that registration of thetool may occur based on the location of the tool at the distinctanatomical landmarks. In other words, as the tip of the tool can bedriven to a known anatomical location in the patient, the 3D Model maythen be rotated by the user to overlay the known anatomical location inthe 3D Model with the fluoroscopy image, in which the known anatomicallocation is visible. Such action will also serve to register the toolwith the 3D Model or localize the tool in the reference frame of the 3Dmodel reference frame AMF.

In another exemplary configuration, instead of, or in addition to,having the user manually rotate the 3D Model to correspond with thefluoroscopy image to line up distinct landmarks visible in both thefluoroscopy image and the 3D Model, the computer 36 may be programmed toemploy a suitable algorithm such as automated geometric search ormathematical optimization techniques configured to match a distinctshape measured by the fiber sensor with a corresponding shape in the 3DModel. In this manner, the tool may also be registered with the 3DModel. The accuracy of this method will depend on the size of vesselthat the tool is in, and the degree of curvature of the tool. Accuracywill be improved if the tool is in a smaller vessel and will be worse ifthe tool is in larger vessels. This automated technique can also be usedin conjunction with the manual techniques described above. For example,the computer may be programmed to do automatic registration and suggesta preferred registration but the user may do final adjustments of themodel. Once the tool is localized in the 3D Model of the patient'sanatomy, the user may then proceed to maneuver the tool in the 3D Model.

Another technique that may be utilized to register the tool to the 3DModel through fluoroscopy system 30 involves the use of radiopaquemarkers. More specifically, radiopaque markers can be fixed to theanatomy. However, these markers would need to be present duringpre-operative imaging when the 3D Model is created, and remain in thesame location during intraoperative fluoroscopy imaging. With thistechnique, the position of these markers in the fluoroscopy referenceframe FF can be used to correlate to the same markers in the 3D Modelreference frame AMF, thereby registering the fiber sensor to the 3DModel reference frame AMF. Three-dimensional angiography may also makeit easier to register the tool to the 3D Model by facilitatingacquisition of the model in realtime, i.e. while the patient is on bed.While the model might drift away from the real anatomy when theoperation is carried out, it may be advantageous to obtain the model andperform operations in the same spot.

Another technique that may be utilized to register the surgical tool toa 3D Model utilizes intravascular imaging. This technique allows for 3Dvisualization of a surgical tool, such as, a catheter, in the anatomy,but without the use of fluoroscopic imaging. Such a technique canbenefit both physicians and patients by improving the ease of toolnavigation, as well as and reducing radiation exposure of personnelinside the operating room.

Turning now to FIG. 8, the registration technique 600 may begin byutilizing a sensor 602 operatively coupled to the tool to sense a shapeof the tool 604 while in the patient. This sensed shape is thenmathematically correlated against features of the vascular model such ascenterlines or walls in which a larger correlation value corresponds toa better match. The correlation can be performed in real-time on eachshape or by batch processing a sequence of shapes. This proposedtechnique assumes that the tool will always follow a uniqueconfiguration through the vasculature, and thus, a global maximum forthe correlation exists. However, the correlation may return many localmaxima since the tool configuration may follow many different pathsbetween fixed distal and proximal ends. Choosing an incorrect maximumintroduces registration error. Furthermore, in some cases, thepre-operative 3D model may differ from the actual vasculature for anumber of reasons, including, for example, patient motion orinaccuracies in pre-operative sensing. Such situations also may lead toregistration error.

Recent advances in intravascular imaging technology have brought aboutsensors 604 that can provide information about the local structure ofvessel walls 606. Such information may be used for shape registrationand environmental mapping. Two examples of these sensors areintravascular ultrasound (IVUS) probes, and optical coherence tomography(OCT). Intravascular ultrasound periodically produces a 2-Dcross-sectional view of the blood vessel either to the sides of thecatheter in standard IVUS or to the front of a catheter inForward-Facing IVUS. Optical Coherence Tomography periodically producesa local 3D view of the vessel into which the tool is inserted. Theimages produced by these technologies may be processed to provide anestimate of a curve or surface representing the vessel wall 606. Thesensors 604 may also determine the location of the catheter's endpointwithin the vascular cross-section. Use of the sensors coupled with thetool 602 to provide shape information coupled with informationobtainable from sensors 604 configured to provide information about thevessel walls 606 can assist in defining the 3D shape of the blood vessel608.

Once the shape of the vessel is defined or otherwise reconstructed usingthe combined sensor data, the shape can be mathematically correlated tothe 3D model 610, thereby registering the tool to the 3D Model 612. Inimplementation, the 3D reconstruction and correlation steps may becombined into a single recursive filtering algorithm. A Bayesian filter(e.g. Extended Kalman Filter (EKF), Unscented Kalman Filter (UKF), orParticle Filter) may be used to develop an estimate of the tool'sposition relative to the pre-op 3D model given both imaging and sensor602 information. The filter's state is a set of points or a parametriccurve representing the position and shape of the tool 602 with respectto the pre-op 3D model, as well as the rate of change of this shape. Foraccurate registration, patient motion may also be taken into account.Thus, the filter's state may also contain warping parameters for thepre-op 3D model. These warping parameters may be evenly distributed, ormay be selected based on the structure of the anatomy around thevasculature. The motion of the structure of the anatomy around thevasculature may be measured using visible light tracking technologiessuch as stereoscopic cameras, structured light tracking technologies,and/or other localization technologies attached to the patient skin.

The recursive filtering algorithm operates by predicting the motion ofthe tool in the 3D model, then performing an update of the filterhypothesis given new sensor measurements. At each time-step, a kinematicmodel of the catheter and control inputs such as current pull-wiretension and displacement may be used to perform the filter's motionupdate. The filter's measurement update may apply a correction to thetool registration and model warping parameters by comparing a predictedvessel wall with the sensed position and orientation of the vessel fromthe imaging and sensor measurements. The update effectively executes thecorrelation between 3-D sensor information and the 3D model. Performingthese correlations repeatedly in a recursive filtering framework mayprovide a real-time catheter position estimate. Furthermore, thefilter's parameters may be tuned such that differences between themeasurements and the model over a small time constant (ms) will lead tochanges in the catheter position estimate in order to filter outhigh-frequency sensor noise. Differences over a large time constant(seconds) may lead to changes in the model's warping parameters.

Thus, once the tool has been registered to the 3D model, the location ofthe tool within the 3D model may be determined, allowing an operator todrive the tool within the vasculature using the 3D model withoutrequiring intra-operative fluoroscopy.

Sensors 604 may also be utilized to sense the environment around thetool. Thus, once the tool is registered to the 3D model, thisenvironmental information, such as, for example, vascular occlusions maybe displayed at the correct position in the 3D Model.

More specifically, after tool registration, the intravascular imagingsensor 604 provides a mechanism to sense and display features of theenvironment surrounding the tool without the use of fluoroscopy. Thereare many ways to display this information. One non-limiting option is tosimply provide a display of a real-time view of the imaging sensor'soutput alongside a view of the catheter's location in the 3D model orsuperimposed on top of the 3D model. Another option may be to analyzethe intravascular image to detect environmental changes. For example,IVUS image processing techniques can be used to detect areas of plaquein the image. This information can be used to annotate the IVUS image inorder to alert the physician to environmental conditions. Since acombination of IVUS and sensor data 602 may provide 3D information onthe structure of these plaque formations, the 3D pre-op model can alsobe annotated. In this way, the existing work that has used IVUS toperform vascular sensing may be leveraged by the combined IVUS andsensor system to provide a 3D view of the environment to the physician.

Exemplary Error Reduction Methods

Turning now to FIGS. 9-11, exemplary systems and methods for reducingmeasurement error, e.g., of an incremental measurement sensor (IMS), isdescribed in further detail. Registration, as described above, isgenerally the mathematical process of computing the orientation andposition of all or portions of a shape (sequence of points) in somecoordinate frame. Registration can fix the orientation and position ofthe fiber at one or more points (for six degrees of freedom ofconstraints at each point) or registration can be carried out with fewerconstraints at a single point or multiple points. Inherently, though,registration is the method of positioning and orienting a sensor framein a reference frame.

For any IMS, one type of registration is to determine the position andorientation of the proximal end (“origin” of the IMS) in thefluoroscopy, or world, coordinate frame and display that to the user inthe virtual environment. By determining the transformation of the“origin” of the IMS to the world coordinate system, the points in theIMS can be transformed and displayed in the world coordinate systemthroughout the procedure. However, the accuracy of this registrationprocedure can be difficult and inadequate for applications that requiresub-mm accuracy at the distal end of the sensor. Inaccuracy will resultif the origin of the IMS moves; if the origin does move, it needs to betracked in the world coordinate frame, which may lead to error. Inaddition, the error inherent in the sensor could cause errors in thesensor measurement. For instance, in a fiber optic shape sensor, thetighter the bends, the less accurate the sensor is. Tight bends that mayoccur early in the path of the fiber either due to mechanical structuresin the device or pathways in the anatomy, cause additional error in theorientation measurement. This orientation error may be magnified by thelever arm of the fiber causing the tip to be inaccurate by centimeters.This is unsuitable for many applications since sub-millimeter accuracyis desired.

Additional Registration Points

In one exemplary approach illustrated in FIG. 9, multiple positions ofregistration along the length of an elongate member 900 may be providedto reduce the error in a sensor 902. In one example, the sensor 902 isan IMS fiber sensor configured to output a position of the elongatemember at the sensor 902. The elongate member, e.g., a catheter, may begenerally fixed at a proximal end 904 such that the position of theproximal end 904 may generally be known. A position of the elongatemember 900 is known at one additional point 906, which is proximal tothe distal portion of the sensor 902. While only one additional point906 is illustrated, any number of additional points proximal to thesensor 902 may be used, as described further below. Using the additionalpiece(s) of information at the point(s) proximal to the sensor 902 maybe used to register the IMS at a position distal of the “origin,” i.e.,at the sensor 902, helping to reduce orientation error propagated fromthe proximal end to a position error in the distal end. The nature ofthe fiber and catheter is that the proximal end is the only place thatthe fiber is attached to the system, but there are a number of ways ofacquiring registration along the length of the fiber.

Registration of a shape or series of points of the IMS sensor 902 can beused to improve registration. This can be performed by acquiring 3Dshapes or obtaining spatial information from 2D images, i.e., of theelongate member 900. For example, a plurality of points 906, 908, 910,and 912 may be employed to determine a shape of the elongate member 900at each of the points 906, 908, 910, and 912, such that a shape orposition of the elongate member 900 is known. There are many sources ofa three-dimensional anatomic model in robotic catheter procedures thatmay be used in this manner. For instance, models could be generated froma rotational angiography, computed tomography scan, or other standardimaging technique. Also, any known shape that the catheter passesthrough could also contribute to registration just as in a 3-D model,such as an engineered semitortuous introducer, a curve in the take-offof the sheath splayer, an anti-buckling device feature, etc. In allthese cases, the catheter and IMS will be passing through a known shapethat can be used to register the position and orientation of a distalportion of the catheter.

Once the catheter is known to pass through a given three-dimensionalshape defined by the points 906, 908, 910, and 912, providing theregistration is an optimization problem to find the most likely positionand orientation of the sensed shape in relation to the model of theelongate member 900. This solution could be completed using manystandard computer graphics matching techniques or posed as a numericoptimization problem.

Another example of other 3D information may be to add other localizationsensors such as an electromagnetic sensor to various critical pointsalong the catheter. More specifically, at least one of the proximalpoints 906, 908, 910, and/or 912 may have an electromagnetic sensor. Thegenerally absolute measurements of position at these locations canreduce any error propagated from the fiber at a portion distal of theposition of any electromagnetic sensors at points 906, 908, 910, and/or912.

Another exemplary method of obtaining additional shape information is touse computer vision techniques on the fluoroscopy images to track thecatheter and then feed that information into the system to improveregistration. Because two-dimensional imaging will provide lessinformation than a 3D model it may not provide as much information toreduce error, but it would likely remove error at least in the plane ofthe image. This registration might also not be needed constantly duringa procedure, but may be used when imaging, e.g., fluoroscopy, is activeand the operator wants more accuracy of the tracked catheter.Accordingly, a position of a proximal portion of the elongate member900, e.g., along points 906, 908, 910, and/or 912 may be visualized in2D and used to increase accuracy of measurements at the sensor 902.

In a way, the above exemplary approaches to optimizing positionmeasurements of the sensor 902 provide an alternate registrationlocation to a proximal portion of the elongate member, e.g., at the baseof the fiber at the splayer attached to the RCM. However, in theseexamples registering a shape to a 3D model does not necessarilycompletely replace the registration at the splayer (not shown in FIG.9). Using an optimization technique that finds the most likely positionand orientation of the sensor given both the anatomical registration andthe distal splayer registration is probably the best way to reduceoverall error and achieve a strong overall pose of the catheter inrelation to the anatomy. This algorithm can also take advantage of anyproximal motion of the catheter, such as shaft insertion, etc. However,this algorithm can be time consuming and computationally intensive,especially when a good starting point is not given. The registration ofthe origin of the IMS could be used as such a starting point.

Another exemplary approach in the case where global registration ofposition is not needed would be to allow the user to designate aspecific position on the catheter that is constrained laterally, e.g.,by the anatomy of a patient. For example, as shown in FIG. 10 anelongate member 1000 is partially inserted into a patient 1100, whoremains generally fixed in position on a table 1102. In this manner, adistal portion 1004 of the elongate member 1000, which includes an IMS1006 for measuring position of the elongate member 1000, is receivedwithin the patient 1100, while a proximal portion 1002 remains outsidethe body of the patient 1100. The insertion site 1008 of the elongatemember 1000 into the patient 1100 is known and is substantially fixed,such that a position of the elongate member 1000 is known at theinsertion site 1008 in at least two dimensions. The insertion site 1008position, at least in two degrees of freedom, could be registered inaddition to the splayer 1010, while the insertion of the elongate member1000 is updated accordingly. With this technique, the orientation of theelongate member 1000 and/or a measurement fiber at this designated‘base’ (i.e., the insertion site 1008) of the shorter effective fiberwould depend on the actual orientation of the fiber (including twist)and the insertion would depend on the commanded fiber insertion.However, the shape distal to the insertion site 1008 could be updatedrapidly and without any error from the shape of the proximal portion1002, which is proximal to the designated base position, i.e., theinsertion site 1008. Accordingly, error in position measurements of theelongate member 1000 anywhere along the distal portion 1004 is greatlyreduced by effectively reducing the measurement length of the IMS 1006.

The above exemplary approach may be particularly advantageous forrelative position display (essentially a coordinate frame not correctlyregistered to the fluoroscopy/anatomical coordinate frames) but mayultimately make it difficult to determine a global position of the tipof the catheter. However, in many applications that do not superimposethe catheter directly over a model of anatomy (or imply perfectregistration) it would be perfectly appropriate.

Selective Filtering

Other exemplary approaches are generally based around the idea thatfiltering is a method of sacrificing responsiveness in the time domainto reduce the shape and position error. For example, an operator of anelongate member may generally be focusing on the distal end of thecatheter during a procedure, and the proximal end will generally bestable and not moving quickly. As a result, selective filtering onproximal shape can be applied to reduce orientation error in theproximal region while the distal region does not filter the signal. Morespecifically, in the example shown in FIG. 9, position data associatedwith the distal region of the elongate member 900 between the points 912and 902 is not filtered, while the position data of a proximal regionbetween points 906 and 912 is filtered. The selective filtering of theproximal region reduces the influence of proximal error by filtering itout (for instance, averaging over multiple time steps) while, the distalportion will be updated as fast as possible using the orientation andposition of the proximal section as a stable base.

In one exemplary illustration, one could average the positions andorientation over time in the global frame, or you could averageincremental changes in orientation over time and then integrate theaveraged orientation changes to yield the final shape. Integrating theincremental changes could be a more accurate average particularly in thecase of a fiber-based measurement system, e.g., FOSSL, because theactual measurement is being determined from an indication of strain,which is proportional to bend angle and orientation. Thus, white noisemay be present on the level of the strain/incremental orientation asopposed to the final incremented position and orientation.

Because the attention of the operator will likely be focused on thedistal tip or portion, the result of proximal filtering will be aresponsive system that exhibits less error. The exact location wherefiltering starts or stops may vary based on the application and it iseven possible to apply a variable level of filtering along the fiberwith the maximum filtering at the proximal end, e.g., between points 906and 912, and the minimum at the distal end, e.g., distal of the point902. In one case when absolute registration is not needed, it is simpleto ignore the proximal portion(s) of the fiber and treat the distalportion of the fiber as a non-grounded shape sensor that can be orientedarbitrarily.

In examples where the proximal end is filtered heavily in relation tothe distal end, it may be useful to detect when the proximal shapechanges significantly in a short period of time, such as a prolapsedcatheter at the iliac bifurcation (a rapid motion of the shaft of thecatheter bulging up into the aorta). This can be accomplished by notingwhen the new catheter shape is significantly different than the filteredshape. In this case, the filtering on the proximal end can be reduced sothat the operator sees the most up to date information and can reactaccordingly. After the proximal shape remains more constant for a periodof time, the filtering can increase, again reducing error at the tip. Toprevent sudden jumps in the rendered data, temporarily-variablefiltering algorithms can be implemented in such a way as to providecontinuity of the filter output, which may increase the appearance ofsmoothness and reduce noise of the measurement.

An anatomical model need not be used to separate distal and proximalupdates of an IMS localization technology. One exemplary approach wouldbe to apply relatively heavy filtering on the proximal end of the fiber,e.g., between points 906 and 912, and light filtering on the distal end,e.g., distal of point 902, as described above. Specific aspects of thissensor when used in a robotic system could modified, such as updatinginsertion immediately without filtering since axially the catheter isrelatively stiff and low in error (assuming the catheter does notbuckle). This is potentially problematic because by filtering differentdimensions at different rates, trajectories can become skewed, producingmeasurement points that do not lie along the true trajectory of thedevice. Additionally, filtering could be accelerated when the proximalmeasurement changes significantly in relation to the filtered version togive more responsive feedback during a prolapsed situation.

It should be noted that instinctiveness computations are often computedfrom orientations propagated from the registered base of the fiber.Instinctiveness refers generally to matching and orientation or alocation of a device such as a catheter with a visualization device thatis used to control the catheter, such as an image of the catheter. Sinceinstinctiveness includes absolute orientation measurements, they may becomputed separate from any intermediate registration or clippingtechniques. On the flip side, because distance does not magnifyorientation errors, there is little or no extra error from the distancefrom the base to the tip of the fiber in instinctiveness measurements.Furthermore, instinctiveness measurements generally do not require afast update rate so it is possible to filter heavily to reduceorientation error and noise.

Turning now to FIG. 11, an exemplary process 999 for determining aposition of a distal portion of an elongate member is illustrated.Process 999 may begin at block 1110, where an incremental measurementsensor may be provided. For example, as described above an elongatedmember 900 may have an IMS 902 positioned along a distal portion of theelongate member 900. In some exemplary approaches, the elongate member900 includes a fiber, which may be employed to determine position and/ororientation data of the elongate member 900. Process 999 may thenproceed to block 1112.

At block 1112, registration data may be applied at one or more proximallocations along the elongated member. For example, as described above aposition of the elongate member 900 at any one or more of points 906,908, 910, and/or 912 may be registered. For example, a proximal positionof one or more proximal locations may be used to increase accuracy ofmeasured data from the IMS 902.

In some examples, one of the proximal locations used to applyregistration data along the elongated member 900 includes a proximalattachment of the elongated member 900, e.g., at a proximal end 904. Theproximal attachment at the proximal end 904 may general fix a portion ofthe elongated member at the first one of the locations. In otherexamples, a position of the proximal location(s) may be determined usingan electromagnetic sensor, or by using a two-dimensional image of theone or more proximal locations, e.g., as obtained by fluoroscopy duringa procedure. In still another example, applying the registration data atthe one or more proximal locations may include constraining a lateralposition of the one or more proximal locations. Merely as one example,as described above an insertion site 1008 associated with a patient 1100may generally constrain an elongate member 1000 laterally at theinsertion site 1008. Accordingly, the generally fixed insertion site1008 indicates a position of the elongate member 1000 in at least twodimensions at the insertion site 1008.

Proceeding to block 1114, a proximal signal of the elongated member maybe selectively filtered, e.g., in relation to a distal signal of theelongated member. Filtering of the proximal signal may occur at adifferent rate than the filtering of the distal signal. In one example,heavier or more intrusive filtering of the proximal signal may beemployed, especially during a procedure where the proximal portion(s) ofthe elongate member do not change rapidly. In some cases, filtering mayinclude averaging an incremental orientation position change in theproximal signal. Moreover, variable filtering methodologies may be used.For example, as described above a heavier filtering methodology may beemployed only during such times that a position of the proximal portionof the elongate member is not rapidly changing position. Upon detectionof a rapid or unexpected change, the filtering of the proximal portionmay cease or be reduced. Filtering at the initially heavier setting mayresume after a predetermined period of time expires, in which theproximal portion of the elongate member maintains a same position ordoes not rapidly change position during such time. Process 999 may thenproceed to block 1116.

At block 1116, a position of the incremental measurement sensor may bedetermined. For example, as described above a position of an IMS 902 maybe determined based at least upon the registration data from the one ormore proximal locations. In this manner, measurement error may bereduced since less incremental error occurs over the length of theelongate member. Alternatively, or in addition, a position of theincremental measurement sensor may be determined based at least upon afiltered proximal signal. In such cases, selectively filtering mayreduce a fluctuation of the determined position of incrementalmeasurement sensor by generally smoothing out position signals relatingto the proximal portion(s) of the elongate member.

CONCLUSION

The methods described above are the examples of registration using knowndata about the location of the catheter in relation to the anatomy. Thefirst example does not include extra localization information while thesecond example assumes some knowledge of the shape of the anatomy orother features along the path of the catheter. Between these examples,there are a number of other ways to get partial registration at one ormore points along the fiber to reduce orientation error propagated downthe fiber.

The exemplary systems and components described herein, including thevarious exemplary user interface devices, may include a computer or acomputer readable storage medium implementing the operation of drive andimplementing the various methods and processes described herein. Ingeneral, computing systems and/or devices, such as user input devicesincluded in the workstation 31 or any components thereof, merely asexamples, may employ any of a number of computer operating systems,including, but by no means limited to, versions and/or varieties of theMicrosoft Windows® operating system, the Unix operating system (e.g.,the Solaris® operating system distributed by Oracle Corporation ofRedwood Shores, Calif.), the AIX UNIX operating system distributed byInternational Business Machines of Armonk, N.Y., the Linux operatingsystem, the Mac OS X and iOS operating systems distributed by Apple Inc.of Cupertino, Calif., and the Android operating system developed by theOpen Handset Alliance.

Computing devices generally include computer-executable instructions,where the instructions may be executable by one or more computingdevices such as those listed above. Computer-executable instructions maybe compiled or interpreted from computer programs created using avariety of programming languages and/or technologies, including, withoutlimitation, and either alone or in combination, Java™, C, C++, VisualBasic, Java Script, Perl, etc. In general, a processor (e.g., amicroprocessor) receives instructions, e.g., from a memory, acomputer-readable medium, etc., and executes these instructions, therebyperforming one or more processes, including one or more of the processesdescribed herein. Such instructions and other data may be stored andtransmitted using a variety of computer-readable media.

A computer-readable medium (also referred to as a processor-readablemedium) includes any non-transitory (e.g., tangible) medium thatparticipates in providing data (e.g., instructions) that may be read bya computer (e.g., by a processor of a computer). Such a medium may takemany forms, including, but not limited to, non-volatile media andvolatile media. Non-volatile media may include, for example, optical ormagnetic disks and other persistent memory. Volatile media may include,for example, dynamic random access memory (DRAM), which typicallyconstitutes a main memory. Such instructions may be transmitted by oneor more transmission media, including coaxial cables, copper wire andfiber optics, including the wires that comprise a system bus coupled toa processor of a computer. Common forms of computer-readable mediainclude, for example, a floppy disk, a flexible disk, hard disk,magnetic tape, any other magnetic medium, a CD-ROM, DVD, any otheroptical medium, punch cards, paper tape, any other physical medium withpatterns of holes, a RAM, a PROM, an EPROM, a FLASH-EEPROM, any othermemory chip or cartridge, or any other medium from which a computer canread.

Databases, data repositories or other data stores described herein mayinclude various kinds of mechanisms for storing, accessing, andretrieving various kinds of data, including a hierarchical database, aset of files in a file system, an application database in a proprietaryformat, a relational database management system (RDBMS), etc. Each suchdata store is generally included within a computing device employing acomputer operating system such as one of those mentioned above, and areaccessed via a network in any one or more of a variety of manners. Afile system may be accessible from a computer operating system, and mayinclude files stored in various formats. An RDBMS generally employs theStructured Query Language (SQL) in addition to a language for creating,storing, editing, and executing stored procedures, such as the PL/SQLlanguage mentioned above.

In some examples, system elements may be implemented ascomputer-readable instructions (e.g., software) on one or more computingdevices (e.g., servers, personal computers, etc.), stored on computerreadable media associated therewith (e.g., disks, memories, etc.). Acomputer program product may comprise such instructions stored oncomputer readable media for carrying out the functions described herein.

With regard to the processes, systems, methods, etc. described herein,it should be understood that, although the steps of such processes, etc.have been described as occurring according to a certain orderedsequence, such processes could be practiced with the described stepsperformed in an order other than the order described herein. It furthershould be understood that certain steps could be performedsimultaneously, that other steps could be added, or that certain stepsdescribed herein could be omitted. In other words, the descriptions ofprocesses herein are provided for the purpose of illustrating certainexamples, and should in no way be construed so as to limit the claims.

Accordingly, it is to be understood that the above description isintended to be illustrative and not restrictive. Many examples andapplications other than the examples provided would be apparent uponreading the above description. The scope should be determined, not withreference to the above description, but should instead be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled. It is anticipated andintended that future developments will occur in the technologiesdiscussed herein, and that the disclosed systems and methods will beincorporated into such future examples. In sum, it should be understoodthat the application is capable of modification and variation.

All terms used in the claims are intended to be given their broadestreasonable constructions and their ordinary meanings as understood bythose knowledgeable in the technologies described herein unless anexplicit indication to the contrary in made herein. In particular, useof the singular articles such as “a,” “the,” “said,” etc. should be readto recite one or more of the indicated elements unless a claim recitesan explicit limitation to the contrary.

The Abstract of the Disclosure is provided to allow the reader toquickly ascertain the nature of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims. In addition, in theforegoing Detailed Description, it can be seen that various features aregrouped together in various examples for the purpose of streamlining thedisclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments require morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive subject matter lies in less than allfeatures of a single disclosed embodiment. Thus the following claims arehereby incorporated into the Detailed Description, with each claimstanding on its own as a separately claimed subject matter.

What is claimed is:
 1. A system comprising: an elongate member extendingbetween a proximal end and a distal end; one or more sensing elementspositioned on the elongate member, the one or more sensing elementsconfigured to provide at least: first data associated with a firstregion of the elongate member, and second data associated with a secondregion of the elongate member; at least one non-transitory computerreadable medium having stored thereon executable instructions; and atleast one processor in communication with the at least onenon-transitory computer readable medium and configured to execute theinstructions to: receive the first data and the second data from the oneor more sensing elements, filter the first data to reduce orientationerror associated with the first region, and determine a shape of theelongate member based on the filtered first data.
 2. The system of claim1, wherein the second data is not filtered, and the at least oneprocessor is configured to execute the instructions to determine theshape of the elongate member based on the second data and the filteredfirst data.
 3. The system of claim 1, wherein the first data is filteredby averaging over multiple time steps.
 4. The system of claim 1, whereinthe first data is filtered by averaging positions and orientations ofthe first region over time in a global frame.
 5. The system of claim 1,wherein the first data is filtered by averaging incremental changes inorientation of the first region, and the shape is determined byintegrating the averaged incremental changes.
 6. The system of claim 1,wherein the first data is filtered in the time domain.
 7. The system ofclaim 1, wherein the at least one processor is further configured toexecute the instructions to: filter the second data, wherein the seconddata is less filtered than the first data; and determine a shape of theelongate member based on the filtered first data and the filtered seconddata.
 8. The system of claim 7, wherein the first data is filtered at ahigher rate than the second data.
 9. The system of claim 1, wherein theat least one processor is further configured to execute the instructionsto: determine a degree of change of shape of the first region; and whenthe determined degree of change exceeds a threshold, reduce thefiltering of the first region.
 10. The system of claim 9, wherein the atleast one processor is further configured to execute the instructions toincrease the filtering of the first data when the degree of change ofthe first region remains below the threshold for a period of time. 11.The system of claim 9, wherein the at least one processor is furtherconfigured to execute the instructions to increase the filtering of thefirst data after a predetermined period of time.
 12. The system of claim1, wherein the at least one processor is further configured to executethe instructions to: determine a degree of change of shape of the firstregion; and when the determined degree of change exceeds a threshold,stop the filtering of the first data.
 13. The system of claim 1, whereinthe at least one processor is further configured to execute theinstructions to implement a temporarily-variable filtering algorithm.14. The system of claim 1, wherein the at least one processor is furtherconfigured to execute the instructions to register a coordinate frame ofthe elongate member to a reference coordinate frame.
 15. The system ofclaim 14, wherein registering the coordinate frame comprises determininga first position of the elongate member.
 16. The system of claim 15,wherein at least one of the one or more sensing elements is anelectromagnetic sensor positioned on the elongate member, wherein theelectromagnetic sensor provides an output from which the first positionof the elongate member is determined.
 17. The system of claim 15,wherein the first position is determined using a fluoroscopic image. 18.The system of claim 1, wherein the at least one processor is furtherconfigured to execute the instructions to register a coordinate frame ofthe elongate member to a coordinate frame of a 3D model.
 19. The systemof claim 1, further comprising: a catheter manipulator operably coupledto the elongate member; a joint arm coupled to the catheter manipulator;and a control console for manipulating the catheter manipulator.